A. Field of the Invention
This invention describes a particle-loaded fibrillated polytetrafluoroethylene web with a reinforcing screen or scrim at least partially embedded therein. Compared to an unreinforced web, this reinforced web can resist a much greater pressure drop across it without deforming and displays greater strength against various mechanical stresses.
B. Description of Related Art
Particle-loaded, non-woven, fibrous articles wherein the non-woven fibrous web can be compressed, fused, melt-extruded, air-laid, spunbonded, mechanically pressed, or derived from phase separation processes have been disclosed as useful in separation science. Web products of non-woven webs having dispersed therein sorbent particulate have been disclosed to be useful as, for example, respirators, protective garments, fluid-retaining articles, wipes for oil and/or water, and chromatographic and separation articles. Coated, inorganic oxide particles have also been enmeshed in such webs. Such webs with enmeshed particles which are covalently reactive with ligands (including biologically-active materials) have also been recently developed.
Numerous examples of PTFE filled with or entrapping particulate material are known in many fields. Many applications for PTFE filled with electroconductive materials are known. These include circuit boards, oil leak sensors, electrical insulators, semipermeable webs, and various types of electrodes. Other such combinations have been used as gasket or sealing materials and wet friction materials. Still others have been used to produce high-strength PTFE films and webs with applications as structural elements and electronic components. Where the particulate has catalytic properties, this type of combination provides a form which can be conveniently handled. U.S. Pat. No. 4,153,661 discloses various particulate distributed in a matrix of entangled PTFE fibrils as being useful in, among other things, electronic insulators and semipermeable webs.
Numerous combinations of PTFE and metals in which the metal is not entrapped within a PTFE matrix are also known. These include PTFE webs completely or partially coated with metal and metal matrices with a network of fibrillated PTFE in the pores thereof. PTFE powder with metal filler has been used (in paste form) as a battery electrode and as a self-lubricating layer coated on bronze bearings. PTFE films coated onto metal films and plates are also known.
Methods of preparing fibrillated PTFE webs have been described in, for example, U.S. Pat. Nos. 4,153,661, 4,460,642, and 5,071,610.
The physical properties of such particle-loaded fibrillated PTFE webs are somewhat limited, however. They do not resist high pressure drops without deforming and have limited strength against mechanical stresses created by, for example, fluid flow, tensile force, mechanical impact, and abrasion.